Astronomy Picture of the Day

A Sun Halo over Utah

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#85661 by @ 12.04.2006 00:00 - nach oben -
A Sun Halo over Utah

Have you ever seen a halo around the Sun?

This fairly common sight occurs when high thin clouds containing millions of tiny
ice crystals cover much of the sky.

ice crystal acts like a miniature lens.

most of the crystals have a similar
elongated hexagonal shape, light entering one crystal face and exiting
through the opposing face refracts 22
which corresponds to the radius of the Sun Halo.

A similar Moon Halo
may be visible during the night.

The picture was taken in Gunlock,

A flock of birds was caught by chance in the foreground.

Exactly how
ice-crystals form in clouds remains under

Lecture: APOD editor to give public talk in Princeton tonight (April 11)

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